Pavement binder and method of making same (LAW441)

Abstract

The present invention provides a method of making storage-stable road paving binders by blending a minor amount of an unsaturated polymer (e.g., having at least one diene monomer) with a major amount of asphalt at an elevated temperature such that the components are sufficiently fluid to blend; treating the asphalt-polymer blend with a sulfonating agent; and stripping the treated asphalt-polymer blend at an elevated temperature with sufficient stripping gas to remove strippable sulfur moieties and to stabilize the resulting stripped, treated blend. The invention also provides asphaltic compositions made by the method. The asphaltic compositions are useful as binders in road paving applications.

What is claimed is: 
     
       1. A method of making a storage-stable asphaltic composition, suitable for use as a pavement binder, comprising the steps of: (a) blending an unsaturated polymer with an asphalt to form a blend of substantially uniform composition;   (b) treating the asphalt-polymer blend obtained from step (a) with a sulfonating agent; and   (c) contacting the treated blend obtained from step (b) with stripping gas to remove strippable moieties, including sulfur-containing strippable moieties.   
     
     
       2. The method of claim 1 wherein the blending step (a) is performed at a temperature of from 120° to 220° C. 
     
     
       3. The method of claim 1 wherein step (b) is performed at a temperature of from 120° to 220° C. 
     
     
       4. The method of claim 1 wherein the sulfonating agent is selected from acyl sulfates, SO 3 , sulfuric acid and oleum having a concentration of from 50 to 115% (relative to 100% H 2  SO 4 ). 
     
     
       5. The method of claim 4 wherein the amount of sulfonating agent in step (b) is from 0.5 to 7.0 weight % (expressed in terms of 98% H 2  SO 4 ) of the weight of polymer-asphalt blend. 
     
     
       6. The method of claim 1 wherein step (c) is performed at a temperature up to 220° C. 
     
     
       7. The method of claim 1 wherein step (c) is performed until stripping gas which has contacted the treated blend is substantially free of sulfur moieties. 
     
     
       8. The method of claim 1 in which the gas-contacting rate in step (c) is from 1 to 20 vol. gas/hour/volume polymer-asphalt blend. 
     
     
       9. The method of claim 1 wherein the blend formed in step (a) contains from 0.01 to 7 weight percent polymer. 
     
     
       10. The method of claim 1 wherein the polymer used in step (a) is a styrene-butadiene copolymer selected from linear and radial diblock and triblock copolymers and random copolymers. 
     
     
       11. The method of claim 1 wherein the asphalt has a penetration (100 g, 5 s, 25° C.), dmm, in the range of from 30 to 550 and a softening point (Ring and Ball) of up to 60° C. 
     
     
       12. The method of claim 1 wherein the blend is stirred and agitated between steps (a) and (b). 
     
     
       13. The method of claim 1 wherein step (c) is commenced before step (b) has been completed. 
     
     
       14. The method of claim 1 comprising step (d) wherein stripping gas from step (c) is treated to remove environmentally undesirable materials therefrom. 
     
     
       15. An asphaltic composition made by a method comprising the steps of: (a) blending an unsaturated polymer with asphalt to form a blend of substantially uniform composition:   (b) treating the asphalt-polymer blend obtained from step (a) with a sulfonating agent; and   (c) contacting the treated blend obtained from step (b) with stripping gas to remove strippable moieties, including strippable sulfur moieties.   
     
     
       16. A bituminous emulsion comprising an emulsion of an aqueous component and the composition of claim 15. 
     
     
       17. An asphaltic material comprising a blend of bitumen and the composition of claim 15. 
     
     
       18. A pavement composition comprising aggregate mixed with the asphaltic composition of claim 15. 
     
     
       19. A pavement composition comprising aggregate mixed with an asphaltic composition, wherein the asphaltic composition comprises a blend of bitumen and the composition of claim 15.